The 250

I remember almost walking out of a demo in London before I asked to try the 250. spendor A7 speakers.
The job was done in about 3 seconds. what an amp.

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Had mine since Dec’85. Not yet felt a need to change it.

Improvements have arrived by changing items before it - and after… :astonished:

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Someone posted a little while back the internal differences of the 250 from cb, olive through to dr. The transformer increases in VA were intresting. The 250 has been an evolving machine since birth.

I believe the big change occurred with the introduction of 250-2. Until then - so CB & Olive eras - the 250 was - essentially- the same.

What were other amps ?

Different transformers surely?

Richard has covered this previously.

Yep. The transformers got a lot larger. Significantly so.

I’ve owned many 250s over the years but the best was a serviced CB250 in Olive clothing with H+F transformer, what an amp…

Then upgraded to the 250DR but this was more of a sideways step never ultimately convinced I made the right choice!

A serviced 300 none DR appeared on the used market, order restored and then some :grin:

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Yes, the transformer increased from 400VA to 500VA in 1984. Then when the NAP250.2 arrived in 2002 the transformer increased to almost 1000VA and used NA007s for both regulation and output. The NAP250DR moved to NA009s.

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1000VA? 250DR transformer is 400VA and 300DR is 500VA?

Ouput figure for the 250-2 was quoted at 400va. What that means in terms of transformer size I have no idea.

Also, the smoothing capacitors got smaller and inferior, but, on the plus side each channel got a pair of capacitors. The original 250 had a pair of capacitor supplying both channels.

It was clearly a deliberate design change to go bigger on the transformer VA side lower the capacitors. As to how that changes the sound I don’t know.

I’m referring to the rating of the transformers used, not the transient power VA rating.

I just looked it up and the NAP250.2 and 250DR use a 1020VA Toroidal transformer, same as the NAP300.

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Capacitor quality improved a good deal since the early days. Naim moved to using smaller caps, but more of them, as they felt they performed better this way.

Hm never heard about 1k VA transformers. Everywhere it’s been talking about the transformer size and I believe even specs on transformer reads 4-500?

The copy on 300DR reads.

A variable speed, virtually noiseless cooling fan is mounted on a large internal heat sink providing long-term stability and the ability to swing a massive 500 VA on transients.

I’ve taken the spec right out the Naim factory bible.

Transient VA is not the same as the transformer VA rating.

But aside from VA, all one need really do is compare the transformer from a NAP250 to one from a NAP250.2 or 250DR. The latter is not far off twice the size and weight.

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Seems like 500DR use a 1100VA transformer. This was news to me since I’ve always thought of it as the transformer size of 4-500VA which translates to around 400W being the extra power for transients for the 80-90W output stage.

Yes, I’m not sure why the slight difference as physically the NAP500 Tx looks similar in some to the one in the 250.2 and 300 and probably weighs the same too. It was always fun during a tour of the factory to stop in the Tx area of stores where the transformers were measured and graded for potential hum, and pick up one of the reject 500 transformers and hand it to one of the tour guests (both hands required). You expect it to be pretty heavy, but the actual weight always took you by surprise.

After having a NAP200 for various years, about 1,5 years ago I took the step towards a 250DR … it has been mentioned that the 272 / 250 combo is some sort of sweet spot, but the 250 will remain in my system for a very long time!

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